Vehicle, in particular a chassis of a bridge-underside inspection apparatus

ABSTRACT

A vehicle is proposed, in particular a chassis of a bridge-underside inspection apparatus, having a frame (1) and road-vehicle wheels. In order to be able to quickly and simply convert such a vehicle into an operational chassis having increased stability, a pneumatically sprung axle unit (3) and, in front of and/or behind this pneumatically sprung axle unit, at least one unsprung auxiliary wheel (7, 8) are arranged on the frame (1). The axle unit (3) has a pneumatically actuated device (4, 5) which is connected to the spring-suspension arrangement and by means of which the frame (1) can be lowered from a top position in which the spring suspension is effective into a bottom position. The auxiliary wheel (7, 8) is lifted from the roadway in the top position of the frame (1) during the road-transport operation and stands on the roadway in the bottom position of the frame (1) during working operation. Supporting rollers (6), which also serve as a slow drive, can be arranged above the wheels of the axle unit (3), (FIG. 1).

DESCRIPTION

The invention relates to a vehicle, in particular a chassis of abridge-underside inspection apparatus, having a frame and road-vehiclewheels. This arrangement starts from a vehicle which moves on publicroads approximately at the speed of a truck.

In the case of so-called self-erecting bridge-underside inspectionapparatuses or similar heavy special apparatuses having a wideprojection, it is known to convert the chassis used for the roadtransport into an operational chassis before the same is put intoworking service, which operational chassis has greater stability than aconventional sprung and pneumatic-tired road vehicle. Further typicalfeatures of the equipment of an operational chassis are aremote-controlled slow drive and remote-controlled or automaticsteering. In a bridge-underside inspection apparatus, the slow driveserves to move the apparatus during working service on a bridge. Thesteering requires only slight angles of lock in order to be able toaccurately follow a predetermined track.

For example, it is known from German Offenlegungsschrift 3,305,384 toconvert a road-transport chassis into an operational chassis by supportsprovided with running rollers being extended down from the frame ontothe roadway, which supports take up most or all of the vehicle weight.In this known chassis the running rollers can be driven slowly and aresteerable. So that the supports can be extended, it is known to attachthem to the frame in a telescopic, hinged or displaceable manner,hydraulic lifting pistons being provided as a drive for the movement.

However, these supports and their operating mechanisms requireconsiderable expediture, especially as the number of supports andrunning rollers should be as large as possible in the interest ofreducing the maximum concentrated loading on the bridge surface.

On the other hand, vehicles, in particular trucks, having pneumaticallyactuated rear axles, in particular pneumatically sprung rear axles, aregenerally known. These axles are mounted on the frame by means of twolongitudinal links in such a way as to be pivotable up and down and aresupported on the frame via two sets of air bellows or cylinderarrangements. By reducing the pressure in the bellows or cylinders, theframe, with or without the load, can be lowered so far that it sits onunsprung stops of the axles. Conversely, by increasing the pressure, theframe can be lifted again and the spring-suspension behavior requiredfor the road journey can be restored. It is known that this change inheight is utilized in order to carry out a quick change of load, forexample to pick up or set down a container standing on stilts.

The object of the invention is to propose a vehicle which performs boththe function of a road-transport chassis and the function of anoperational chassis, requires relatively low investment costs and can bechanged over quickly and simply from one type of operation to the other.

This object is achieved according to the invention by a vehicleaccording to patent claim 1.

The essential difference between this vehicle and known convertiblechassis for bridge-underside inspection apparatuses or similarappliances is that the unsprung auxiliary wheels, at least under load,are not vertically adjustable on the frame; on the contrary, the frameis lowered until these auxiliary wheels come in contact with the ground.Likewise in contrast to the prior art, the frame is not lowered by meansof devices which are allocated to the auxiliary wheels but with the aidof the pneumatically sprung axle unit. Standard axle units which are onthe market can be used, which standard axle units are relativelyinexpensive, and special lifting devices on the auxiliary wheels areunnecessary.

The maximum lift of pneumatically actuated height-adjustment devices ofstandard truck axles is normally only about 12 cm. But that issufficient, for the same rubber-tired wheels as in the pneumaticallysprung axle units are also conveniently used as auxiliary wheels.Therefore if the auxiliary wheels briefly touch the ground now and againduring the road journey as a result of unevenness or in the event ofextremely pronounced spring deflection of the sprung wheels, this doesno harm. The auxiliary wheels then simply run with the sprung wheels.

The pneumatically sprung axle unit can consist of one or more axles. Thenumber of auxiliary wheels is determined by the stability required. Asingle auxiliary wheel may possibly be sufficient. Two auxiliary wheelsare better, of which one is arranged in front of the axle unit and onebehind the axle unit, and in fact preferably on the side facing thebridge edge during the working operation of the bridge-undersideinspection apparatus. It is even more advantageous to provide at leastone auxiliary axle having two auxiliary wheels. This auxiliary axle canalso be attached in front of or behind the pneumatically sprung axleunit; or one auxiliary axle can be attached in front of thepneumatically sprung axle unit and one auxiliary axle behind it. Theauxiliary wheels preferably run in the same track as the wheels of thesprung axle unit.

So that the operational chassis can be steered in working service, it isproposed that at least one auxiliary wheel or one auxiliary axle bedesigned to be steerable. A simple steering device is sufficient, sinceonly small angles of lock are required. A steering device is convenientwhich normally assumes a middle position and, upon a "left" or "right"signal, makes predetermined fixed angles of lock. Furthermore, theauxiliary wheels are suitable for the arrangement of a slow drive.

If the auxiliary wheels or auxiliary axles are not fastened to the framein a vertically adjustable manner, the ground clearance of the sameduring the road journey is determined by the lifting height of thepneumatically actuated lowering device However, if a greater groundclearance is desired by way of exception, an adjusting device can beattached to the relevant auxiliary axle, by means of which adjustingdevice this axle can be moved unloaded between two positions atdifferent heights and can be locked on the frame in these positions.Simple manually actuated adjusting devices in particular can beconsidered here. Their attachment can also be worthwhile inasmuch as theselection of a pneumatically sprung axle unit having a relatively smallstroke is more cost-effective.

The abovementioned fixed stops of the axles of the pneumatically sprungaxle unit onto which the frame comes down during lowering are locatedrelatively far to the inside, i.e. at a small distance from thelongitudinal center plane of the vehicle. The supporting base of theframe on these axles during tilting in the transverse direction istherefore substantially smaller than the track width. An importantfurther development of the invention then consists in an axiallyparallel supporting roller being arranged on the frame above at leastone wheel of the axle unit, against which supporting roller the tiretread of the relevant wheel abuts in the bottom position of the frame. Aplurality of supporting rollers can also be provided for one wheel. Themain advantage of these supporting wheels consists in the fact that thetilting edge of the frame relative to the axles is shifted outward andthe stability of the frame is thereby considerably increased. A furtheradvantage of such supporting rollers consists in the fact that they canbe equipped with a slow drive, for example a slow hydraulic drive. Thesupporting rollers then act as driving friction wheels on therubber-tired wheels. The supporting rollers do not touch the tiresduring road-transport operation.

A further means of increasing the stability of the frame during workingoperation consists in the auxiliary wheels having tires with a harderspring-suspension behavior than the tires of the wheels of the axleunit. The tires can, for example, be expanded with plastic. If need be,the auxiliary wheels or some of them can be extendable in the axialdirection so that the parking base can thereby be increased. The heightof the auxiliary wheels and the stops on the frame is convenientlyselected in such a way that the total axle load is uniformly distributedover the available axles when the frame is lowered into the bottomposition.

The proposed vehicle can be designed as a self-propelled truck, as atrailer or as a semi-trailer. In the two first-mentioned cases, thesteerable axle can also be used for steering during working operation.Apart from being used for a bridge-underside inspection apparatus, sucha vehicle can also be used for mobile lifts, portable high-level workingplatforms or for machines doing mechanical work, e.g. road-makingmachines.

Two exemplary embodiments of the invention are described below withreference to the drawing, in which, in particular:

FIG. 1 shows the side view of a truck on which a bridge-undersideinspection apparatus is erected, in the road-transport position,

FIG. 2 shows the side view of this vehicle with lowered frame ready forworking operation,

FIG. 3 shows the side view of a bridge-underside inspection apparatusdesigned as a semi-trailer, in the road-transport position with tractorvehicle,

FIG. 4 shows the side view of this apparatus ready for workingoperation.

FIG. 5 to a smaller scale, shows the side view of the chassis accordingto FIG. 4 with set-up bridge-underside inspection apparatus during useon a bridge,

FIG. 6 shows a schematic cross-section of such a vehicle in the area ofthe pneumatically sprung axle unit, the frame being located togetherwith supporting rollers in the top position, and

FIG. 7 shows the representation according to FIG. 6 with lowered frame.

The truck according to FIGS. 1 and 2 has a frame 1 designed as a flatplatform and has a total of five axles which are provided withrubber-tired wheels of the same size, as are normally used forroad-transport vehicles of this type. The front axle 2 is steerable andsprung in the conventional manner. The two center rear axles are thedrive axles. They form an axle unit 3 having pneumatic spring suspensionand a device for vertical adjustment. The two abovementioned axles arepivotably linked to the vehicle frame by means of longitudinal links 4.The air-filled spring bellows are indicated by 5. An axially parallelsupporting roller 6 is arranged at a distance of about 12 cm above eachof the four wheels of the axle unit 3. These supporting rollers can beslowly driven by means of rotating hydraulic motors. Located in front ofand behind the axle unit 3 are auxiliary axles 7 and 8 respectivelywhich are attached to the frame 1 in a fixed manner, i.e. not in aspring-mounted manner. The auxiliary wheels run in the track of thewheels of the axle unit 3. The wheels of the auxiliary axles 7 and 8 sitso high that they are at a distance of about 12 cm from the roadwaysurface.

The bridge-underside inspection apparatus attached to the frame 1essentially consists of a lifting tower 9 and a working catwalk 10 whichis tilted through 90° so that its floor is vertical. The lifting towerhas a bottom tower section 12 which can be rotated about the tower axisby means of a slewing ring 11. The working catwalk 10 is linked to thistower section 12 in such a way as to be pivotable about a transverseaxis 13. The lifting tower 9 is displaceably mounted in the longitudinaldirection on a guide frame 14. This guide frame is linked to a hingedframe 17 by means of parallel levers 15 and 16. This hinged frame 17 isin turn mounted on a swivelling bolster 19 in such a way as to bemovable about a horizontal transverse axis 18, which swivelling bolster19 rotates on the frame 1 about a vertical axis 20.

With the folded bridge-underside inspection apparatus and the threesprung pneumatic-tired axles according to FIG. 1, the vehicle issuitable for road-transport operation. The supporting rollers 6 areclear and the wheels of the auxiliary axles 7 and 8 have no contact withthe ground. Before the bridge-underside inspection apparatus is set up,the vehicle is prepared according to FIG. 2 by lowering the frame 1 forthe working position. By reducing the air pressure in the spring bellows5, the same are compressed under the weight of the loaded frame andbecome shorter. The frame sinks down until the auxiliary wheels come incontact with the ground and are loaded. The bearing blocks 21 of thelongitudinal links have also been lowered with the frame 1, and thesupporting rollers 6 press on the tires of the axle unit 3. The totalaxle load of the rear vehicle section therefore spreads from two to fouraxles.

FIGS. 6 and 7 show in particular the supporting rollers 6 more clearly.These supporting rollers 6 have a continuous shaft 22 and are designedin such a way that they can absorb the considerable radial forces of thewheels (here designated by 23) of the axle unit 3. During the loweringas a result of reducing the air pressure in the spring bellows 5, thetop stops 24 fixed to the frame 1 come into contact with the bottomstops 25 fixed to the axle. This means that, in the loweredposition--despite the supporting rollers 6--the outer lateral limitedges of the stops 24, which limit edges run in the longitudinaldirection of the vehicle, are the determining tilting edges of thevehicle body. As a result of the loaded supporting rollers 6 accordingto FIG. 7, these tilting edges are shifted laterally outwardsapproximately by the distance a. The supporting rollers therefore makean important contribution to the stability of such an apparatus duringworking operation.

Apart from that, the friction contact between the supporting rollers andthe wheels 23 is used for the slow movement of the vehicle on thebridge. The hydraulic motors (not shown) acting on the supportingrollers can also be remotely controlled from the working catwalk. Thefront axle 2, which can be equipped with a remote-control attachment, isused for the steering.

FIGS. 3 to 5 show as a second exemplary embodiment a semi-trailer onwhich an identical bridge-underside inspection apparatus is erected. InFIG. 3, the frame 26, likewise designed as a platform, is in the topposition for road transport. The tractor vehicle 27 is coupled on. Thesemi-trailer has four axles. The two rear axles form a pneumaticallysprung axle unit 28. A firmly attached auxiliary axle 29 is locateddirectly in front of this axle unit 28, and, at a distance furtherforward, a further likewise unsprung auxiliary axle 30 is provided inthe area of the offset portion of the semi-trailer neck. This auxiliaryaxle 30 is steerable and in addition is attached to short longitudinallevers 31 which, by means of a small hydraulic lifting cylinder 32 or amanually actuated winch, can be adjusted between a top and bottomposition so that this auxiliary axle 30 can be lowered and lifted byabout 10 cm. For the road-transport journey, it is located in its topposition so that a ground clearance of 22 cm results. The auxiliary axle29 has a ground clearance of 12 cm. The axle unit 28 is sprung. Asupporting roller 33 above the last wheel and a supporting-roller pair34 above the penultimate wheel are disengaged.

The tractor vehicle 27 is uncoupled in such a way that first of all theauxiliary axle 30 is moved into its bottom position and locked so thatboth auxiliary axles have the same ground clearance of 12 cm. Thepneumatically actuated lowering devices on both the tractor vehicle andthe axle unit 28 are now actuated. Thus all four axles of thesemi-trailer take up the total axle load, as FIG. 4 shows. The tractorvehicle 27 can move away. The supporting rollers which have a slowhydraulic drive in this example too, are in engagement. With the simplesteering device of the auxiliary axle 30, the vehicle can follow thepredetermined track on the bridge.

In order to move the bridge-underside inspection apparatus into itsworking position according to FIG. 5, the swivelling bolster 19 (seeFIG. 1) is rotated about its vertical axis 20, and at the same time thehinged frame 17 is swung up about its axis 18, and in fact by means of alifting cylinder which is indicated by chain-dotted line. The bottompart 12 of the tower thus travels over the parapet of the bridge andswings increasingly further downward. In addition, the parallel arms 15,16 can also be swung away from the hinged frame 17 likewise by means ofa lifting cylinder indicated by chain-dotted line. When the swivellingbolster 19 has reached its 90° position and the lifting tower 9 isvertical, the working catwalk 10 is swung laterally about the axis 13into the horizontal and then swung through 90° under the bridge by meansof the slewing ring 11. FIG. 5 shows this working position.

A multiplicity of variants of the axle arrangements described in theseexamples is possible. The semi-trailer could, for example, have a sprungaxle unit with three axles. An auxiliary axle could also be arrangedbehind the axle unit, in which case the front auxiliary axle 30, whichcan be lifted free of load, could be omitted depending on thelongitudinal position of the center of gravity of the vehicle. In thiscase, one or more auxiliary axles ought to be steerable. More or lessaxles could also be provided on the truck. The steerability of the rearauxiliary axle behind the sprung axle unit would also be advantageous.

1--Frame

2--Front axle

3--Axle unit

4--Longitudinal link

5--Spring bellows

6--Supporting roller

7--Auxiliary axle

8--Auxiliary axle

9--Lifting tower

10--Working catwalk

11--Slewing ring

12--Tower section

13--Transverse axis

14--Guide frame

15--Parallel lever

16--Parallel lever

17--Hinged frame

18--Transverse axis

19--Swivelling bolster

20--Vertical axis

21--Bearing block

22--Shaft

23--Wheel

24--Stop

25--Stop

26--Frame

27--Tractor vehicle

28--Axle unit

29--Auxiliary axle

30--Auxiliary axle

31--Longitudinal lever

32--Lifting cylinder

33--Supporting roller

34--Supporting-roller pair

a--Distance

I claim:
 1. A vehicle, in particular a chassis of a bridge-underside inspection apparatus, having a frame and road-vehicle wheels, wherein a pneumatically sprung axle unit (3) is provided with at least one axle which has a pneumatically actuated device (4, 5) which is connected to the spring-suspension arrangement and by means of which the frame (1) can be lowered from a top position in which the spring suspension is effective into a bottom position in which the frame rests unsprung on supporting stops (24, 25) of the axles of this axle unit, and wherein at least one unsprung auxiliary wheel is arranged on the frame (1) in front of and/or behind the axle unit (3), which auxiliary wheel is lifted from the roadway in the top position of the frame, is lowered together with the frame (1) and, in the bottom position of the frame, stands on the roadway and takes up a portion of the total axle load.
 2. The vehicle as claimed in claim 1, wherein at least one auxiliary axle (7, 8) is provided with two auxiliary wheels.
 3. The vehicle as claimed in claim 1, wherein at least one auxiliary wheel is steerable.
 4. The vehicle as claimed in claim 2, wherein one auxiliary axle (30) has an adjusting device (31, 32) by means of which it can be moved unloaded between two positions at different heights and can be locked on the frame (26) in these positions.
 5. The vehicle as claimed in claim 1, which comprises a design as a semi-trailer (FIG. 3).
 6. The vehicle as claimed in claim 1, wherein at least one of the wheels has a slow drive.
 7. The vehicle as claimed in claim 1, wherein an axially parallel supporting roller (6) is arranged on the frame (1) above at least one wheel of the axle unit (3), against which supporting roller (6) the tire tread of the wheel abuts in the bottom position of the frame.
 8. The vehicle as claimed in claim 7, wherein a plurality of supporting rollers (34) are provided for one wheel.
 9. The vehicle as claimed in claim 7, wherein the supporting roller can be driven slowly.
 10. The vehicle as claimed in claim 1, wherein the auxiliary wheels have tires with a harder spring-suspension behavior than the tires of the wheels of the axle unit. 